Motion reproducing mechanism



y 30, 1946- w. H. NEWELL MOTION REPRODUCING MECHANISM Filed Sept. 24, 1942 4 Sheets-Sheet 1 INVENTOR WuJJA H.NEWELL.

ATTORNEY July 30, 1946.

W. H. NEWELL MOTION REPRODUCING MECHANISM Filed Sept. 24, 1942 4 Sheet s-Sheet 2 INVENTOR %ILLIAM H.NEWELL dT QW' ATTORNEY 4 Sheets-Sheet 3" INVENTOR WlLLlAM H NsweLL ATTORNEY MOTION REPRODUCING MECHANISM Filed Sept. 24, 1942 July 30, 1946. w. H. NEWELL 2,405,046

MOTION REPRODUGING MECHANISM Filed Sept. 24, 1942 4 Sheets-Sheet 4- IN VEN TOR %ULL1AM H.NEWELL.

A TTORNE Y Patented July 30, 1946 MOTION REPRODUCING MECHANISM William H. Newell, New York, N. Y., assignor to Ford Instrument Company, Inc., Long Island City, N. Y., a corporation of New York Application September 24, 1942, Serial No. 459,581

8 Claims. 1

The invention relates to motion reproducing or following mechanism where the movement of a primary element is to be reproduced in a secondary or following element, and particularly to such mechanisms in which the transmission system operates a control member for a power unit termed a servomotor.

The invention is typically embodied and will be explained in connection with electric self-synchronous transmission systems, and is designed to meet the requirement of correct synchronization in systems that employ a two speed transmission.

In such systems the motion of the member that is to be reproduced at a distance is transmitted at two difierent ratios and is received by a high speed and a low speed receiver known commonly as the fine and coarse receivers. These receivers are arranged in joint control of the servomotor, the fine receiver having control so long as the error, that is, the positional discrepancy between the elements, is within a certain limit, and the coarse receiver takes control when the error exceeds that limit.

In the mechanism of this invention the energizing circuit of the servomotor includes two sets of contacts connected in parallel and one controlled by each receiver, and a circuit breaker operated by the coarse receiver opens the fine control circuit when the coarse receiver takes over the control. A feed back from the servomotor opens the contacts when the controls are satisfied, that is, it opens the coarse control contacts when the error is less than the stated limit, and it opens the fine control contacts when the two elements are in positional agreement.

In accordance with this invention the contacts of both the fine and coarse controls are of such a character that they will absorb limited errors and will gradually erase the error at a controlled rate when the condition which produced the error there will be a positional error until the biasing means restores the yielding contact to its biased position.

Braking or resisting means, however, control the rate at which the error is erased so that the follower is brought smoothly into synchronism.

Since both the fine and coarse controls are thus equipped the return to synchronism is controlled irrespective of the degree of error.

Due to the fact that the two controls have different ratios of movement, the characteristics of the resisting means to dampen the return movement of the control contacts must be such as to satisfy the individual requirements. In other words resisting means must permit of more rapid movement of the fine control contacts than of the coarse control contacts, in order to get the proper relative speed of the follower element.

For this purpose it is satisfactory to use a magnetic drag for the fine control which requires comparatively rapid rotation to generate a retarding force which is proportional to the rate of motion. For the coarse control a pneumatic damper is suitable, the escape orifice of which is properly adjusted.

Other objects and advantages of the invention will appear from the following description of the embodiment of the invention illustrated in the accompanying drawings.

Fig. 1 is a side elevation of a complete receiver assembly embodying the invention.

Fig. 2 is a sectional elevation of the same on the plane indicated by the line 22 in Figs. 1 and 3.

Fig. 3 is a plan of the same.

Figs. 4, 5, 6 and '7 are sectional plans of the coarse control mechanism in the planes indicated by the lines 44, 55, 65 and 'l-'l, respectively, in Figs. 1 and 2.

Fig. 8 is a diagram of the electrical circuits.

Essentially the assembly consists of a coarse receiver motor I and a fine receiver motor 2 of an electrical synchronous transmission system, an electric servomotor 3 and coarse and fine controls for the servomotor. These elements are secured upon a mounting plate 4.

The coarse receiver motor I and the fine receiver motor 2 are connected to coarse and fine transmitters of the electrical synchronous transmission system. The transmission system is not shown as it may be of any suitable type, the only requirement being that the coarse and fine transmitters be driven at a definite ratio, for example, the coarse transmitter may make one revolution for thirty-six revolutions of the fine transmitter. A suitable two speed transmission system is shown in Patent 1,122,942.

The fine receiver 2 is of the flange mounted type and the coarse receiver l is of the ball bearing mounted type. In other words the stator of the former is fixed while the stator of the latter is rotatable. The shaft 5 of the fine receiver rotor may be considered the fine primary element and the shaft 6 of the coarse receiver rotor may be considered the coarse primary element. These rotors will rotate at different ratios to the movement that is to be reproduced by the follower element, for example, the coarse receiver rotor having a 1 to 1 ratio and the fine receiver rotor a 36 to 1 ratio thereto, this ratio being the same as that between the coarse and fine transmitters. These receiver rotors operate controls for the servomotor.

The servomotor 3 is a single phase, condenser type, induction motor having a squirrel-cage rotor i. The two legs 8 and 9 of the stator winding have a common connection ill with one side of a single phase line H, the other side being connected to the inner contact of each receiver control, as will later be described. The opposite ends of the legs 8 and 9 of the stator winding are connected to the outer contacts of the receiver controls by leads l2 and it, as will be described, and a condenser is is connected across the leads I2 and it. Therefore when the inner contact of either control is against one of the outer contacts, one leg of the stator winding is connected directly to the line wire and the ther leg is connected to it through the condenser. This completes an approximate two phase circuit and the rotor turns clockwise or counterclockwise, depending upon which connection is made.

Telescoping partially over the upper end of the fine receiver 2 is an inverted cup-shaped bearing member l5 that is secured to the mounting plate 5 and has secured on its top a similar bearing member iii of smaller diameter. Within the hearing member it are housed the elements of a ma netic drag. A quirrel-cage rotor i! has trunnions i8 and it: on its opposite ends which are vertically disposed in line with rotor shaft 5, the trunnion it bearing in the top of bearing member it and trunnion i9 bearing in the top of bearing member I5. A collar 20 couples shaft 5 with trunnion i9. Therefore rotation of the fine receiver rotor produces rotation of the squirrel-cage rotor l'i.

Rotatively mounted in the rotor ll of the magnetic drag is a magnetized cylindrical member 25 the axis of which turns in the trunnion I8 as a bearing and has on its upper end a contact arm 22 that carries the inner double contact 23 of the fine control, the outer contacts 24 being mounted to be moved by the servomotor in response to the incoming movement. The precise construction for accomplishing this will be described later.

The rotor l?! of the drag device drives the contact arm 22 through a yieldable connection. The hub of a heart cam 25 is secured to the trunnion iii. A roller 23, urged in contact with the heart cam, is carried by the follower arm 21 that is pivoted at one end on a plate 28 the hub of which bears on trunnion l8 on top of the housing it, and the free end of the arm is urged toward the heart cam by a holding spring 29 attached to a lug on the opposite edge of the plate 23.

The contact arm 22 is connected to the plate 28 by centering springs 3d. The contact arm is spaced above the plate and the springs are therefore attached at their outer ends to upstanding arms 35 on opposite corners of the plate, their inner ends being attached to the outer end of the contact arm 22.

The outer contacts 24 are positioned with refore controlled.

spect to the inner contact 23 by the servomotor 3, the shaft 32 of which may be considered the secondary or following element which is to reproduce the movement of the primary elements 5 and 3. In other words the incoming movement operates the primary contact of the servomotor control to close the energizing circuit; and the response of the servomotor moves the secondary contacts to open the circuit.

Surrounding the bearing member [6 and bearing thereon through anti-friction bearings, as shown, is a slip ring supporting drum 33 which has a top flange on which the outside contacts 24 are carried by contact arms 34. A flange on the bottom of the drum 33 is provided with spur gear teeth which mesh with a spur gear 35 on the shaft 32 of the servomotor. Rotation of the shaft therefore rotates the drum and hence the secondary contacts 24 in the proper ratio of movement.

The drum 33 is provided with three slip rings 33a, 33b and 330 which are engaged by brushes in a holder on an arm 36 supported from the mounting plate 4. The center contact 23 is connected to the ring 33a the brush of which is connected to one ide of the line through a circuit breaker under the control of the coarse control, as will be described, and the outer contacts 23 are connected to the rings 33b and 330. The brushes of rings 33b and 330 are connected with leads 23 and i2, respectively. Through this arrangement when the receiver is energized, movement of the inner contact against an outer contact causes the servomotor to drive the slip ring assembly in such manner that the inner contact tends to be centered between the outer contacts.

The function of the magnetic drag is to increase stability of operation and reduce the synchronizing time by its action on the inner contact arm. If the movement of the outer contacts synchronizeswith that of the inner contact, the movement of the arm 22 with that of the rotor I7 is unimpeded and the arm 22 remains centralized by the springs 30. If the movement of the secondary contacts lags for any reason, such as acceleration, the centralizing springs will allow the arm 22 to rotate relative to the rotor H to absorb the error or lack of agreement, and one of the centralizing springs is placed under a tension proportional to the error. When the servomotor gets up to speed and starts to erase the error, the magnetic drag develops an opposing torque on the arm 22 proportional to the speed of the member 2! in the rotor l1, and the return movement of the contact arm is there- It follows therefore that the servomotor must attain ynchronization with the fine receiver at a gradually decreasing rate. Consequently the servomotor has little tendency to overrun or hunt.

The freedom of movement of the contact arm 22 relative to the plate 28 is limited by stops 31 which are upstanding arms on the edge of the plate 28 disposed on opposite sides of the arm 22 in equally spaced relation thereto. There- ,fore the displacement of the arm 22 by pressure tion of displacement greater than that within the limits of the stops 3'! is also proportional to the extent of displacement.

The coarse receiver control takes over when a predetermined error has accumulated. It is satisfactory, for example, to allow the fine receiver to be one-third of a rotation out of agreement when the coarse receiver contacts close. If the ratio is 36 to 1, then the accumulated error in the coarse receiver will be 3 degrees. This means that the follower element will be 3 degrees out of agreement with the movement to be fol owed when the coarse receiver takes control.

Si ce the coarse receiver motor I is of the ball bearing mounted type, the response of the servomotor turns the stator of the receiver, thus differentially neutralizing the rotation of the magnetic field, wherefore the rotation of the shaft 5 represents the difference between the incoming impulse and the response. When there is no error the receiver rotor and hence the shaft 5 has no rotation, Angular movement at the proper ratio is imparted to the stator of receiver by the servomotor shaft 32 by bevel gears 38 and worm and worm wheel 9. The proper ratio for the gearing between the drum and the worm wheel 39 is the same as the ratio between the coarse and fine transmitters and the coarse and fine receivers, that is, 35 to l.

The rotor of the coarse receiver drives an arm carrying the inner or primary contacts of the coarse control through a heart cam. This arm after a movement of a predetermined amount, say 3 degrees, opens the fine control circuit and at the same time or, preferably, slightly before, touches one or the other of the outside or secondary contacts of the coarse control and closes the coarse control circuit. In this case, as will be seen. it is the carrier for the outside contacts that is made to yield to absorb an error and that is retarded in its return from a displaced position so that the error is erased at a rate proportional to the error and the operation is uniform and stable as it passes from the coarse to the fine control.

The inner contact arm is an upstanding member 40, T-shape in cross-section and carrying two double contacts at different levels, the lower contacts 4: being energizing contacts engageable with outer energizing contacts 42 on scissor arms 43 urged toward each other by a spring 44. The upper contacts 45 on the inner contact arm 49 are engageable with outer control contacts 4% on a pivoted control arm 4'! centralized by springs 48.

The inner contact arm 43 is secured at its lower end on a plate 49 secured on a hub rotatively bearing on the rotor shaft 5. A heart cam 59 is also secured on the hub above the plate 43, and an arm 51 is secured on the end of the shaft 6 and extends across the heart cam. A roller arm 52 which. carries the follower roller is urged toward the cam by a spring 53 which connects the arms 5| and 52. This yieldable heart cam drive causes the arm 49 to follow the' movement of the shaft 6 within the limits of movement of the arm after which the spring 53 yields and allows the roller to ride up on the cam.

At the top of the coarse control is a pneumatic damper 54 supported on the mounting plate 4 and closed at its lower end by a plate 55. Depending from. this plate 55 are two hexagonal posts 56 which support a plate 51 on their lower ends. This plate has a bearing post 58 for the scissor arms 63 and it supports a central fixed contact 59 engageable with outer movable contacts 6i! carried by insulated conductive strips 6| on the arms 43, the contacts ea suitably extending through holes in the arms, as indicated in Fig. 8. A predetermined movement of arm 4 will cause contact 4! to engage one or the other of contacts 32 and move one of contacts til away from contact 59.

Slip ring 33a is connected to one of the contact strips 6! by lead 62, and the other contact strip 6% is connected to one side of the line by lead 53. Therefore when the scissor arms are closed the inner contact 23 of the fine control is connected with the line, but the movement of the rotor of the coarse receiver enough to move one of the scissor arms breaks that connection.

Lead $3 is also connected with post 58 and therefore the contacts A2 are live contacts. The outside contacts of the control arm 4? are connected to leads l2 and E3 in parallel with slip rings 33c and 33b and hence in parallel with the outer contacts 24 of the fine control. The arm 49 acts as a connector to connect the outside energizing contacts 42 with the outside control contacts 45.

The outer ends of the centralizing springs G8 are attached to pins M5 that depend from the top plate 55, and they allow the arm $7 and hence the outer control contacts to yield under pressure of the arm lf as the error accumulates and t to absorb the error. This creates a return toroue proportional to the error. This torque is ted by the pneumatic damper 54 which performs much the same function as the magnetic drag.

The pneumatic damper consists of two moving vanes interleaved with two stationary vanes 6'3 so as to form nearly air'tight compartments between adiacent sides of the vanes. The whole is a cylindrical unit, the stationary vanes being secured to the inner wall of the cylindrical casing. The moving vanes are integral with an axial hub 67 that turns on trunnions bearing in the plate 55 and in the top plate 68 of the damper housing. The control plate 41 is fastened on a reduced extension of the bottom trunnion. Therefore the plate 4:? and the movable vanes move together.

Air flow from one compartment of the damper to another is permitted by vent holes 69 in the stationar vanes. the rate of flow being regulated by two screws ti diametrically opposite in the cylindrical casing. By turning in the vent screws the vent holes are constricted and the damping torque is increased. The torque exerted by the pneumatic damper is balanced by the pull of the centering springs, and hence the error decreases at a rate proportional to its magnitude.

From the above it is evident that coarse control is obtained through movement of the inner contact arm 39. When the servomotor output differs sufliciently from the received movement, for example, by more than /1 revolution of the rotor of the fine receiver motor, the inner contact arm 48 displaces one of the scissor arms. This action disconnects th'e fine control by opening the connection between the contact 58 and one of the contacts 65, and simultaneously energizes the coarse control through one of the contacts 45. The air gap between the inner and outside energizing contacts and also between the inner and outside control contacts will be properly adjusted for the desired result. The circuit breaker contacts 59, act as a stop to the inward movement of contacts 42 under the tension of the spring 44.

The pneumatic damper allows but n of a. turn of the rotor of the coarse receiver, and if the aeoaoec error exceeds that amount, the inner control contact is held continuously against an outer control contact by the action of the heart cam relief, and the servomotor drives at full speed to reduce the error.

It is obvious that changes may be made in the construction shown in the drawings and above particularly described within the principle and scope of the following claims.

I claim:

1. Following mechanism comprising in combination with two primary elements, one fine and one coarse, having a predetermined ratio of relative movement and a following element, a servomotor for actuating the following element, an energizing circuit for the servomotor having a fine control and a coarse control, each control including a primary and a secondary contact member, the respective contact members being connected in parallel and the primary contact members being movable by the respective primary elements to close the contacts, means actuated by the servomotor to open the contacts, one of the contact members of each control being yieldable under the pressure of its cooperative contact member to allow the contact members toadjust themselves to the relative positions of the primary and following elements and thereby to absorb error in positional relation of the elements, means biasing the yieldable contact members in the direction to remove error, and means in each control for retarding the return movement of its yieldable contact member.

2. Following mechanism comprising in combination with two primary elements, one fine and one coarse, having a predetermined ratio of relative movement and a following element, a servomotor for actuating the following element, an energizing circuit for the servomotor having a fine control and a coarse control, each control including a primary and a secondary contact member, the respective contact members being connected in parallel and the primary contact members being movable by the respective primary elements to close the contacts, a circuit breaker in series with the primary contact member of the fine control arranged under the control of the primary contact member of the coarse control, means actuated by the servomotor to open the contacts, one of the contact members of each control being yieldable under the pressure of its cooperative contact member to allow the contact members to adjust themselves to the relative positions of the primary and following elements and thereby to absorb error in positional relation of the elements, means biasing the yieldable contact members in the direction to remove error, and means in each control for retarding the return movement of its yieldable contact member.

3. Following mechanism comprising in combination with two primary elements, one fine and one coarse, having a predetermined ratio of relative movement and a following element, a servomotor for actuating the following element, an energizing circuit for the servomotor having a fine control and a coarse control, each control including a primary and a secondary contact member, the respective contact members being connected in parallel and the primary contact members being movable by the respective primary elements to close the contacts, means actuated by the servomotor to open the contacts, one of the contact members of each control being yieldable under the pressure of its cooperative contact member to allow the contact members to adjust themselves to the relative positions of the primary and following elements and thereby to absorb error in positional relation of the elements, means biasing the yieldable contact members in the direction to remove error, drag means in the fine control including a member attached to the yieldable contact member and opposing its return movement by a torque proportional to the rate of that movement, and a pneumatic damper attached to the yieldable contact member of the coarse control and retarding its return movement.

4. Following mechanism comprising in combination with two primary elements, one fine and one coarse, having a predetermined ratio of relative movement and a following element, a servomotor for actuating the following element, an energizing circuit for the servomotor having a fine control and a coarse control, each control including a primary and a secondary contact member, the respective contact members bein connected in parallel and the primary contact members being movable by the respective primary elements to close the contacts, means actuated by the servomotor to open the contacts, one of the contact members of each control being yieldable to absorb error in positional relation of the elements, means biasing the yieldable contacts in the direction to remove error, magnetic drag means connecting the fine primary element with the yieldable contact member of th fine control and opposing its return movement by a torque proportional to the rate of that movement, and a pneumatic damper attached to the yieldable contact member of the coarse control and retarding its return movement.

5. Following mechainsm comprising in combination with two primary elements, one fine and one coarse, having a predetermined ratio of relative movement and a following element, a servomotor for actuating the following element, an energizing circuit for the servomotor having a fine control and a coarse control, each control including a primary and a secondary contact member, the respective contact members being connected in parallel and the primary contact members being movable by the respective primary elements to close the contacts, a circuit breaker in series with the primary contact member of the fine control arranged under the control of the primary contact member of the coarse control, means actuated by the servomotor to open the contacts, one of the contact members of each control being yieldable to absorb error in positional relation of the elements, means biasing the yieldable contacts in the direction to remove error, magnetic drag means connecting the fine primary element with the yieldable contact member of the fine control and opposing its return movement by a torque proportional to the rate of that movement, and a pneumatic damper attached to the yieldable contact member of the coarse control and retarding its return movement.

6. Following mechanism comprising in combination with two primary elements, one fine and one coarse, having a predetermined ratio of relative movement and a following element, an electric servomotor for actuating the following element, an energizing circuit for the servomotor having a fine control and a coarse control, each control including a pair of outside contacts and an inner contact, the respective contacts being connected in parallel, a movable contact arm carrying the inner contact of each control, a yieldable drive connection between the fine primary element and the contact arm of the fine control, means biasing the latter contact arm to central position, means for retarding the return movement of the latter contact arm to central position when displaced therefrom, a pair of spring arms connected to one side of the energizing circuit and having each an energizing contact, a circuit breaker in serie with the inner contact of the fine control and arranged to be operated by the spring arms, the contact arm of the coarse control being disposed between and engageable with the spring arms and having an energizing contact cooperative with those on the spring arms, a drive connection between the coarse primary element and the contact arm of the coarse control, a yieldable control arm carrying the outside contacts of the coarse control, mean biasing the control arm to central position, and means for retarding the return movement of the control arm to central position when displaced therefrom.

7. Following mechanism comprising in combination with two primary elements, one fine and one coarse, having a predetermined ratio of relative movement and a following element, an electric servomotor for actuating the following element, an energizing circuit for the servomotor having a fine control and a coarse control, each control including a pair of outside contacts and an inner contact, the respective contacts being connected in parallel, a movable contact arm carrying the inner contact of each control, a drive connection between the fine primary element and the contact arm of the fine control including magnetic drag means opposing the return movement of the contact arm to central position when displaced therefrom by a torque proportional to the rate of movement, means biasing the fine control contact arm to central position, a pair of spring arms connected to one side of the energizing circuit and having each an energizing contact, a circuit breaker in series with the inner contact of the fine control and arranged to be operated by the spring arms, the contact arm of the coarse control being disposed between and engageable with the spring arms and having an energizing contact cooperative with those on the spring arms, a drive connection between the coarse primary element and the contact arm of the coarse control, a yieldable control arm carrying the outside contacts of the coarse control, mean biasing the control arm to central position, and means for retarding the return movement of the control arm to central position when displaced therefrom.

8. Following mechanism comprising in combination with two primary elements, one fine and one coarse, having a predetermined ratio of relative movement and a following element, an elecric servomotor for actuating the following element, an energizing circuit for the servomotor having a fine control and a coarse control, each control including a pair of outside contacts and an inner contact, the respective contacts being connected in parallel, a movable contact arm carrying the inner contact of each control, a drive connection between the fine primary element and the contact arm of the fine control including magnetic drag means opposing the return movement of the contact arm to central position when displaced therefrom by a torque proportional to the rate of movement, means biasing the fine control contact arm to central position, a pair of spring arms connected to one side of the energizing circuit and having each an energizing contact, a circuit breaker in series wtih the inner contact of the fine control and arranged to be operated by the spring arms, the contact arm of the coarse control being disposed between and engageable with the spring arms and having an energizing contact cooperative with those on the spring arms, a drive connection between the coarse primary element and the contact arm of the coarse control, a yieldable control arm carrying the outside contacts of the coarse control, means biasing the control arm to central position, and a pneumatic damper attached to the control arm and retarding its return movement.

WILLIAM H. NEWELL. 

